Pattern forming method using charged particle beam process and charged particle beam processing system

ABSTRACT

A pattern forming method using an improved charged particle beam process, and a charged particle beam processing system prevent effectively the corrosion of a workpiece by a reactive gas adsorbed by and adhering to the surface of the workpiece when the workpiece is taken out into the atmosphere after pattern formation. The charged particle beam processing system comprises, as principal components, an ion beam chamber provided with an ion beam optical system, a processing chamber provided with a gas nozzle through which a reactive gas is blown against a workpiece, a load-lock chamber connected through a gate valve to the processing chamber. The load-lock chamber is capable of producing a plasma of an inert gas for processing the surface of the workpiece by sputtering. The workpiece is returned to the load-lock chamber after a pattern has been formed thereon in the processing chamber by reactive processing including irradiating the surface of the workpiece with a charged particle beam in an environment of the reactive gas, and the workpiece is subjected to a plasma process to remove the reactive gas adsorbed by the workpiece during pattern formation and adhering to the workpiece.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 08/788,421, filedJan. 27, 1997, now U.S. Pat. No. 5,976,328 the subject matter of whichis incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to a pattern forming method using acharged particle beam process, and a charged particle beam processingsystem and, more specifically, to a pattern forming method using acharged particle beam process and suitable for preventing the corrosionof a workpiece by a reactive gas when minutely processing the workpieceby using a charged particle beam and the reactive gas, and improvementsin a charged particle beam processing system.

A charged particle beam, such as a focused ion beam or an electron beam,can be focused in a beam of a very small diameter. Fine processing ofwiring patterns of semiconductor devices, such as LSI circuit devices,for the correction of the wiring patterns of semiconductor devices andthe analysis of defects in semiconductor devices can be achieved byusing the energy of a charged particle beam. Since fine processing usinga charged particle beam is a sputtering process in which atoms or groupsof atoms of the materials of the workpiece are caused to sputter by theimpingement of the charged particle beam on the surface of theworkpiece, the processing speed of the fine processing is relativelylow, the selectivity of the fine processing in terms of the material ofthe sample, i.e., a workpiece, is relatively low, and it is verydifficult to stop processing at a desired layer in a workpiece of alaminated structure having a plurality of layers of different materials.

Active studies have been made in recent years on processing techniquesusing a reactive gas and a charged particle beam, such as a focused ionbeam or an electron beam, in combination. These processing techniquesactivate a reactive gas by the energy of a charged particle beam toinduce a chemical reaction. Therefore, these processing techniquesenable the rapid etching of a workpiece, and is capable of stoppingprocessing at a desired layer of a material in a laminated structure byselectively using a reactive gas suitable for processing the layers ofdifferent materials of the workpiece.

A technique relating to a processing system using such a processingmethod is disclosed in JP-A No. 1-169860.

Although a pattern forming method (process) using, in combination, areactive gas and a charged particle beam is capable of rapid processing,some reactive gases are highly corrosive to metals. For example, Ifchlorine gas (Cl₂ gas) is employed as a reactive gas in processing aworkpiece made of aluminum (Al), Cl₂ gas adsorbed by the workpieceremains on the surface of the workpiece even if the supply of Cl₂ gas isstopped. Therefore, the Cl₂ gas retained on the surface of the workpieceby adsorption reacts with moisture contained in the atmosphere when theworkpiece carrying the Cl₂ gas is taken into the atmosphere, corrodesthe Al workpiece and damages processed portions of the Al workpiece.

Nothing about the processing of the reactive gas adsorbed by theworkpiece is considered by the prior art.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to solve problemsin the foregoing prior art and to provide a pattern forming methodemploying improved charged particle beam processing and a chargedparticle beam processing system capable of preventing the corrosion of aworkpiece by a reactive gas retained on the surface thereof byadsorption when the workpiece is taken out from the processing chamberinto the atmosphere.

The foregoing object can be achieved by a method (a) which forms adesired pattern in a processing chamber by etching a layer formed on aworkpiece by a reactive process using, in combination, a reactive gasand a charged particle beam, and subjects the surface of the workpieceto a plasma sputter processing using a plasma of an inert gas beforetaking out the workpiece from the processing chamber into theatmosphere, a method (b) which heats a workpiece by a heating device,such as a heater or a lamp, a method (c) which coats the surface of aworkpiece with a carbon film before subjecting the workpiece to areactive pattern forming process, and removes the carbon film remainingon the surface of the workpiece by oxygen plasma ashing, a method (d)which forms a pattern by irradiating a workpiece with a charged particlebeam while oxygen gas is blown against the surface of the workpiece inthe atmosphere of a reactive gas or a method (e) which forms a patternon a workpiece by irradiating the workpiece with both an oxygen beam anda charged particle beam.

The method (a) processes the workpiece by a plasma of an inert gasbefore taking out the workpiece from the processing chamber into theatmosphere by a plasma processing method which supplies an inert gas,such as Ar gas or N₂ gas, at a flow rate of 10 sccm, maintains thepressure in a processing chamber at 133 Pa, exerts power of 200 W and13.56 MHz on the inert gas to produce the plasma, and exposes thesurface of the workpiece to the plasma for 3 to 5 min for light plasmasputter processing. The plasma is produced by high-frequency dischargeor microwave discharge.

In this method, which subjects the workpiece to plasma sputterprocessing using the plasma of the inert gas before taking out theworkpiece from the processing chamber into the atmosphere, the followingreactions take place when the workpiece is exposed to the plasma.

(1) The workpiece is heated and, consequently, the reactive gas adsorbedby and adhering to the surface of the workpiece is forced to separatefrom the workpiece by heat.

(2) The reactive gas adsorbed by and adhering to the surface of theworkpiece is forced to separate from the workpiece by the impact appliedthereto by the plasma.

(3) The material forming the workpiece is oxidized and the chemicalresistance of the workpiece against the reactive gas is enhanced.

These reactions purge the surface of the workpiece of the reactive gasadhering thereto and hence the workpiece will not be corroded when takenout from the processing chamber into the atmosphere.

The method (b) heats the workpiece at a temperature that purges thesurface of the workpiece of the reactive gas adhering thereto and,consequently, the workpiece will not be corroded when taken out from theprocessing chamber into the atmosphere. The method (b) heats theworkpiece in an evacuated environment maintained at a vacuum on theorder of 1 to 5×10⁻⁴ Pa by a heating means, such as a heating device topurge the surface of the workpiece of the reactive gas, such as Cl₂ gas,adhering thereto. Practically, it is preferable that the workpiece isheated at a temperature in the range of, for example, 150 to 250° C. Theworkpiece may be heated in an environment of an inert gas, such as N₂gas, instead of in an evacuated environment for the same effect.

The method (c) coats the surface of the workpiece with a carbon film andhence the reactive gas is adsorbed by the carbon film. Therefore,portions of the material of the workpiece other than those irradiatedwith the charged particle beam do not react on the reactive gas, and theworkpiece can perfectly be purged of the reactive gas by removing thecarbon film by an oxygen plasma ashing process subsequent to thereactive gas process. The carbon film may be formed so as to coverregions in the surface of the workpiece other than those in which apattern is formed. Practically, the thickness of the carbon film isseveral hundreds angstroms. It is desirable to form the carbon film inthe least necessary thickness.

Although the carbon film can be formed by a sputtering process, it ispractically preferable to form the carbon film by a plasma CVD processbecause a pattern forming system is suitable for the plasma CVD process.Although residual portions of the carbon film remaining on the workpieceafter a pattern has been formed may be left unremoved if the purpose ofapplication permits, usually, it is desirable to produce an oxygenplasma and to burn and evaporate the carbon film by exposing theworkpiece to the oxygen plasma (oxygen plasma ashing). The reactive gasadhering to the carbon film is removed together with the carbon filmfrom the workpiece.

The method (d), which irradiates the workpiece with a charged particlebeam while oxygen gas is blown against the surface of the workpiece, andthe method (e), which irradiates the workpiece with an oxygen beam,oxidize the surface of the workpiece by the agency of the oxygen gas andremove the reactive gas adhering to the surface of the workpiece by theimpact given thereto by the charged particle beam. Therefore, theworkpiece will not be corroded when taken out from the processingchamber into the atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a charged particle beamprocessing system in a first embodiment according to the presentinvention;

FIG. 2 is a schematic sectional view of a charged particle beamprocessing system in a second embodiment according to the presentinvention;

FIG. 3 is a schematic sectional view of a charged particle beamprocessing system in a third embodiment according to the presentinvention;

FIG. 4 is a schematic sectional view of a charged particle beamprocessing system in a fourth embodiment according to the presentinvention; and

FIG. 5 is a schematic sectional view of a charged particle beamprocessing system in a fifth embodiment according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be describedhereinafter with reference to the accompanying drawings.

First Embodiment

A charged particle beam processing system in a first embodimentaccording to the present invention and a pattern forming method to becarried out by the same charged particle beam processing system will bedescribed with reference to FIG. 1.

(1) Charged Particle Beam Processing System

An ion beam and an electron beam, as charged particle beams, aresubstantially the same in processing effects. In the followingdescription, the charged particle beam is supposed to be a focused ionbeam by way of example.

Referring to FIG. 1, an ion beam optical system is disposed in an ionbeam chamber 6 formed in an ion beam vessel. The ion beam optical systemcomprises an ion source 1 (Ga in this embodiment), lenses 3 and 4 forfocusing an ion beam 2 emitted by the ion source 1, and a deflector 5for deflecting the ion beam 2. The components of the ion beam opticalsystem are controlled by a power source and a controller, not shown.

An evacuating device, not shown is connected by a discharge pipe 7 tothe ion beam chamber 6 to evacuate the ion beam chamber 6 at a vacuum. Athrough hole is formed in a bottom wall of the ion beam vessel definingthe ion beam chamber 6 so that the ion beam 2 is able to travel throughthe through hole and the flow of a reactive gas into the ion beamchamber 6 is limited to the least possible extent.

A main vessel defining a processing chamber 18 is joined to the bottomof the ion beam vessel defining the ion beam chamber 6. Disposed in theprocessing chamber 18 are a workpiece holder 9 on which a workpiece 8 ismounted, an X-Y stage 10 capable of moving along the X- and the Y- axis,a gas nozzle 13 for blowing a reactive gas against the workpiece 8, anda secondary particle detector having, for example, a photomultiplier 11and a scintillator 12 in combination. The processing chamber 18 isevacuated to a vacuum through a discharge pipe 19 by an evacuatingdevice, not shown.

A signal provided by the secondary particle detector comprising thephotomultiplier 11 and the scintillator 12 by amplifying a signalprovided upon the detection of secondary particles is processed by anamplifier and a signal processing circuit, not shown, synchronizing witha deflecting signal for deflecting the ion beam 2 to form an image ofsecondary particles on the surface of the workpiece 8 for theobservation of a surface being processed.

The gas nozzle 13 is connected through valves 14 and 16, and a flowregulator 15 to a gas cylinder 17 containing a reactive gas.

A load-lock chamber 28 is connected through a gate valve 20 to theprocessing chamber 18. The holder 9 is carried into the load-lockchamber 28 by a conveying system, not shown. Disposed within theload-lock chamber 28 are a lower electrode 21 for supporting the holder9, connected to a HF power source (high-frequency power source) 22, andan upper electrode 23 disposed opposite to the lower electrode 21 andconnected to a ground. A predetermined inert gas is supplied from aninert gas cylinder 27 through valves 24 and 26, and a flow regulator 25into the load-lock chamber 28. The load-lock chamber 28 serves as aplasma splutter processing chamber in which the workpiece 8 issputtering processed by a plasma of the inert gas.

(2) Pattern Forming Method Using the Charged Particle Beam ProcessingSystem

A pattern forming method including a charged particle beam process to beexecuted by the charged particle beam processing system shown in FIG. 1will specifically be described hereinafter.

In the following description, it is supposed that the workplace 8 is asilicon wafer having a surface coated with an Al thin film, the reactivegas is Cl₂ gas, the inert gas is Ar gas, and the Al thin film isprocessed in a predetermined pattern by a charged particle beam process.

The workpiece holder 9 holding the workpiece 8 is placed in theload-lock chamber 28, the load-lock chamber 28 is evacuated to a vacuumby the evacuating device, not shown, and then the gate valve 20 isopened to transfer the workpiece holder 9 from the load-lock chamber 28onto the X-Y stage 10 disposed in the processing chamber 18. Then, theion source 1 projects the ion beam 2, the lenses 3 and 4 focus the ionbeam 2, and the deflector 5 deflects the focused ion beam 2 to scan thesurface of the workpiece 8 with the focused ion beam 2.

Positions and regions on the surface of the workpiece 8 to be processedare determined through the observation of an image of the surface of theworkpiece 8 formed by amplifying detection signals provided through thedetection of secondary electrons discharged from the surface of theworkpiece 8 by the secondary particle detector comprising thephotomultiplier 11 and the scintillator 12. Then, the valves 14 and 15are opened to supply Cl₂ gas, i.e., the reactive gas, from the reactivegas cylinder 17 at a predetermined flow rate regulated by the flowregulator 15 to the gas nozzle 13. Cl₂ gas is blown through the gasnozzle 13 against the surface of the workpiece 8.

While Cl₂ gas is being blown through the gas nozzle 13 against thesurface of the workpiece 8, the predetermined regions on the surface ofthe workpiece 8 are scanned with the ion beam 2 for reactive processingto form a desired pattern. After the desired pattern has been formed byreactive processing, the radiation of the ion beam 2 is stopped, thevalves 14 and 16 are closed to stop supplying Cl₂ gas.

Subsequently, the gate valve 20 is opened, the holder 9 is transferredfrom the processing chamber 18 through the gate valve 20 onto the lowerelectrode 21 disposed within the load-lock chamber 28. Then, the gatevalve 20 is closed to isolate the load-lock chamber 28 from theprocessing chamber 18, the valves 24 and 26 are opened to supply Ar gas,i.e., the inert gas, at a flow rate of several tens standard cubiccentimeters per minute regulated by the flow regulator 25 from the inertgas cylinder 27 into the load-lock chamber 28.

Upon the stabilization of the flow rate of Ar gas and the pressure inthe load-lock chamber 28, the HF power source 22 applies a HF voltage(high-frequency voltage) to the lower electrode 21. Consequently, an Arplasma is produced in a space between the holder 9 and the upperelectrode 23, and the surface of the work piece 8 is bombarded with Ar⁺ions, whereby the surface of the workpiece 8 is purged of Cl₂ gasadhering thereto by the impact of Ar⁺ ions.

At the same time, the workpiece 8 exposed to the plasma is heated, andthe heat generated in the workpiece 8 promotes the separation of Cl₂ gasfrom the workpiece 8. After thus purging the surface of the workpiece 8of Cl₂ gas adhering thereto for a predetermined time, the application ofthe HF voltage by the HF power source 22 to the lower electrode 21 isstopped to stop the ionization of Ar gas, the valves 24 and 26 areclosed to stop supplying Ar gas into the load-lock chamber 28. Then, theworkpiece 8 is taken out from the load-lock chamber into the atmosphere.The reaction of Cl₂ gas with moisture contained in the atmosphere, whichmay occur unless the workpiece 8 is purged of Cl₂ adhering thereto, doesnot occur and hence the workpiece 8 is not corroded.

Although the first embodiment employs the HF power source as a means forproducing the plasma, a discharge means employing a microwave may beused for the same purpose and the same effect.

The reactive gas may be a halogen gas corrosive to metals other than Cl₂gas, such as Br₂ gas, I₂ gas or F₂ gas, and the inert gas may be N₂ gasinstead of Ar gas. A plasma produced by ionizing oxygen gas may be usedfor the plasma process.

In the first embodiment, the surface of the workpiece 8 is subjected toa plasma cleaning process using the etching action of an Ar gas plasmain the load-lock chamber 28 to remove moisture and such adhering to thesurface before feeding the workpiece 8 into the processing chamber 18.Then the workpiece thus cleaned is subjected to a reactive process forforming a pattern in the processing chamber 18. Since the surface of theworkpiece 8 is cleaned and impurities including moisture are removedfrom the surface of the workpiece 8 before the workpiece 8 is subjectedto the reactive process, the corrosion of the surface of the workpiece 8by the reaction of the reactive gas blown against the surface of theworkpiece 8 with moisture which may otherwise be remaining on thesurface of the workpiece 8 does not occur.

Second Embodiment

A charged particle beam processing system in a second embodimentaccording to the present invention and a pattern forming method to becarried out by the same charged particle beam processing system will bedescribed with reference to FIG. 2.

(1) Charged Particle Beam Processing System

The charged particle beam processing system in the second embodimentshown in FIG. 2 is provided with a load-lock chamber 28 different inconstruction from that of the first embodiment and is substantially thesame in other respects as the charged particle beam processing system inthe first embodiment. A holder support 29 for supporting a workpieceholder 9 is disposed in the load-lock chamber 28, a heater 30 isincorporated into the holder support 29, and the heater 30 is connectedto a heater power source 31. The heater power source 31 supplies powerto the heater 30 to heat a workpiece 8 held on the workpiece holder 9.

(2) Pattern Forming Method Using the Charged Particle Beam ProcessingSystem

Similarly to the pattern forming method using the charged particle beamprocessing system in the first embodiment, the pattern forming methodusing the charged particle beam processing system in the secondembodiment places the workpiece 8 in a processing chamber 18, andirradiates desired positions and desired regions in the surface of theworkplace 8 with an ion beam 2 while Cl₂ gas, i.e., a reactive gas,supplied from a reactive gas cylinder 17 is being blown against thesurface of the workpiece 8 placed in the processing chamber 18 forreactive processing to form a desired pattern. After the desired patternhas been formed, the workpiece holder 9 holding the workpiece 8 istransferred through a gate valve 20 into the load-lock chamber 28 and ismounted on the holder support 29.

The load-lock chamber 28 is evacuated by an evacuating device, notshown, and is maintained at a vacuum on the order of 1×10⁻⁴ Pa, theheater power source 31 is connected to the heater 30 to heat theworkpiece 8 at a temperature in the range of, for example, 150 to 250°C. As the workpiece 8 is heated, Cl₂ gas adhering to the surface of theworkpiece 8 is forced to separate from the surface of the workpiece 8 byheat. Therefore, workpiece 8 taken out from the load-lock chamber 28into the atmosphere does not carry any Cl₂ gas and hence the workpiece 8is not corroded by the reaction of Cl₂ gas with moisture contained inthe atmosphere.

The workpiece 8 may be heated for the same effect in an environment ofan inert gas, such as N₂ gas, instead of in a vacuum.

Third Embodiment

A charged particle beam processing system in a third embodimentaccording to the present invention and a pattern forming method to becarried out by the same charged particle beam processing system will bedescribed with reference to FIG. 3.

(1) Charged Particle Beam Processing system

The charged particle beam processing system in the third embodimentshown in FIG. 3 is provided with a load-lock chamber 28 different inconstruction from that of the first embodiment and is substantially thesame in other respects as the charged particle beam processing system inthe first embodiment. A holder support 32 for supporting a workpieceholder 9 holding a workpiece 8 is disposed in the load-lock chamber 28,and an opening is formed in an upper wall of a vessel defining theload-lock chamber 28 and is covered with a quartz plate 33. Theworkpiece 8 held on the workpiece holder 9 mounted on the holder support32 is heated through the quartz plate 33 by a mercury vapor lamp 34disposed above the holder support 32. Thus, the third embodiment employsthe mercury vapor lamp 34 instead of the heater 30 employed in thesecond embodiment.

(2) Pattern Forming Method Using the Charged Particle Beam ProcessingSystem

Similarly to the pattern forming method using the charged particle beamprocessing system in the first embodiment, the pattern forming methodusing the charged particle beam processing system in the thirdembodiment places the workpiece 8 in a processing chamber 18, andirradiates desired positions and desired regions in the surface of theworkplace 8 with an ion beam 2 while Cl₂ gas supplied from a reactivegas cylinder 17 is being blown against the surface of the workpiece 8placed in the processing chamber 18 for reactive processing to form adesired pattern. After the desired pattern has been formed, theworkpiece holder 9 holding the workpiece 8 is transferred through a gatevalve 20 into the load-lock chamber 28 and is mounted on the holdersupport 29.

The load-lock chamber 28 is evacuated by an evacuating device, notshown, and is maintained at a vacuum on the order of 1×10⁻⁴ Pa, and thenthe mercury vapor lamp 34 is turned on.

The workpiece 8 absorbs light emitted by the mercury vapor lamp 34 andgenerates heat. Cl₂ gas adhering to the surface of the workpiece 8 isforced to separate from the surface of the workpiece 8 by the thermalenergy. The separation of Cl₂ gas from the surface of the workpiece 8 ispromoted by light energy. Therefore, workpiece 8 taken out from theload-lock chamber 28 into the atmosphere does not carry any Cl₂ gas andhence the workpiece 8 is not corroded by the reaction of Cl₂ gas withmoisture contained in the atmosphere.

The workpiece 8 may be heated for the same effect in an environment ofan inert gas, such as N₂ gas, instead of in a vacuum environment.

An infrared lamp may be employed instead of the mercury vapor lamp 34for heating the workpiece 8 for the same effect.

Although the workpiece 8 is heated in the load-lock chamber in thesecond and the third embodiment, the processing chamber 18 may beprovided with a heating means like that employed in the second or thethird embodiment to heat the workpiece 8 for the same purpose and thesame effect.

Fourth Embodiment

A charged particle beam processing system in a fourth embodimentaccording to the present invention and a pattern forming method to becarried out by the same charged particle beam processing system will bedescribed with reference to FIG. 4.

(1) Charged Particle Beam Processing System

As shown in FIG. 4, the charged particle beam processing system in thefourth embodiment is provided with a load-lock chamber 28 the same inconstruction as that of the first embodiment shown in FIG. 1. Thecharged particle beam processing system in the fourth embodiment is thesame in construction as that in the first embodiment except that acylinder 27 corresponding to the inert gas cylinder 27 of the firstembodiment contains oxygen gas, and a methane gas cylinder 38 isconnected through valves 35 and 37 and a flow regulator 36 is connectedto a load-lock chamber 28 in the fourth embodiment. The fourthembodiment is the same in other respects as the first embodiment.

(2) Pattern Forming Method Using the Charged Particle Beam ProcessingSystem

A workpiece holder 9 holding a workpiece 8 is mounted on a lowerelectrode 21 disposed in the load-lock chamber 28. The load-lock chamber28 is evacuated by an evacuating device, not shown, to a vacuum and theload-lock chamber 28 is maintained at the vacuum.

Then, the valves 35 and 37 are opened to supply methane gas at a flowrate of several tens standard cubic centimeters per minute regulated bythe flow regulator 36 from the methane gas cylinder 38 into theload-lock chamber 28. Upon the stabilization of the flow rate of methanegas and the pressure in the load-lock chamber 28, a methane gas plasmais produced by applying a HF voltage to the lower electrode 21 by a HFpower source 22 to deposit a carbon film over the surface of theworkpiece 8 by a plasma CVD process.

The thickness of the carbon film thus formed in on the order of severalhundreds angstroms. After the carbon film of a desired thickness hasbeen formed, the valves 35 and 37 are closed to stop supplying methanegas into the load-lock chamber 28. Subsequently, a gate valve 20 isopened to transfer the workplace holder 9 holding the workpiece 8 fromlower electrode 21 disposed in the load-lock chamber 28 to a stage 10disposed in a processing chamber 18.

Then, similarly to the pattern forming method using the charged particlebeam processing system in the first embodiment, the pattern formingmethod irradiates desired positions and desired regions in the surfaceof the workpiece 8 with an ion beam 2 while Cl₂ gas supplied from a gascylinder 17 is being blown against the surface of the workpiece 8 toform a desired pattern on the surface of the workpiece 8.

After all the processes for forming the pattern have been completed, theworkpiece holder 9 holding the workpiece 8 is returned through the gatevalve 20 onto the lower electrode 21 in the load-lock chamber 28. Then,the gate valve 20 is closed, the load-lock chamber 28 is evacuated to avacuum on the order of 1×10⁻⁴ Pa by an evacuating device, not shown,valves 24 and 26 are opened to supply oxygen gas at a flow rate on theorder of several tens standard cubic centimeters per minute regulated bya flow regulator 25 from the gas cylinder 27 into the load-lock chamber28.

Subsequently, a HF voltage is applied to the lower electrode 21 by a HFpower source 22 to produce an oxygen gas plasma in the space between theworkpiece holder 9 and an upper electrode 23 connected to a ground toremove the carbon film from the surface of the workpiece 8 by a plasmaashing process. Since Cl₂ gas adheres to the carbon film, Cl₂ gas isremoved together with the carbon film from the workpiece 8.

Consequently, the workpiece 8 will not be corroded by the reaction ofCl₂ gas with moisture contained in the atmosphere when the workpiece 8is taken out from the load-lock chamber 28 into the atmosphere. Althoughthe fourth embodiment uses methane gas for forming the carbon film, ahydrocarbon gas other than methane gas, such as ethane gas, may be usedinstead of methane gas.

Fifth Embodiment

A charged particle beam processing system in a fifth embodimentaccording to the present invention and a pattern forming method to becarried out by the same charged particle beam processing system will bedescribed with reference to FIG. 5.

(1) Charged Particle Beam Processing System

As shown in FIG. 5, a reactive gas cylinder 17 containing a reactive gasand a oxygen gas cylinder 42 containing oxygen gas are connected to agas nozzle 13 disposed in a processing chamber 18. The reactive gassupplied through valves 14 and 16 and a flow regulator 15 to the gasnozzle 13 and the oxygen gas supplied through valves 39 and 41 and aflow regulator 40 to the gas nozzle 13 are blown against a workpiece 8.The charged particle beam processing system in the fifth embodiment isthe same in other respects as that in the first embodiment.

(2) Pattern Forming Method Using the Charged Particle Beam ProcessingSystem

A workpiece holder 9 holding the workpiece 8 is transferred from aload-lock chamber 28 onto a stage 10 disposed in a processing chamber10. Desired positions and desired regions in the surface of theworkpiece is irradiated with an ion beam 2 while Cl₂ gas, i.e., thereactive gas, is being blown against the surface of the workpiece toform a desired pattern by a reactive processing.

Then, the valves 14 and 16 are closed to stop supplying Cl₂ gas, andthen the valves 39 and 41 are opened to blow oxygen gas supplied at aflow rate on the order of several standard cubic centimeters per minuteregulated by the flow regulator 40 against regions in the surface of theworkpiece 8 around the regions of the same processed by reactiveprocessing, and then the ion beam 2 is deflected by a deflector 5 forscanning.

The regions in the surface of the workpiece 8 against which Cl₂ gas wasblown must be scanned with the ion beam 2. Cl₂ gas blown through the gasnozzle 13 against the surface of the workpiece 8 spreads in areas ofwidths in the range of 2 to 3 mm around lines forming the pattern and itis difficult to irradiate those areas with the ion beam 2 by a singleirradiation cycle. Therefore, the irradiation cycle is repeated severaltimes to irradiate all the areas in the surface of the workpiece 8necessary to be irradiated with the ion beam 2 or the stage 10 is movedproperly while the ion beam 2 is moved along the lines forming thepattern. When the surface of the workpiece 8 is thus irradiated with theion beam 2 in the environment of oxygen gas, Cl₂ gas adhering to thesurface of the workpiece 8 is forced to separate from the surface of theworkpiece 8 by the agency of oxygen gas and the energy of the ion beam2. Consequently, the workpiece 8 will not be corroded by the reaction ofCl₂ gas with moisture contained in the atmosphere when the workpiece 8is taken out from the load-lock chamber 28 into the atmosphere.

The charged particle beam processing system in the fifth embodiment canbe constructed simply by providing the processing chamber of aconventional charged particle beam processing system with an oxygen gassupply means for supplying oxygen gas into the processing chamber, andan oxygen gas blowing means for blowing oxygen gas against the surfaceof a workpiece placed in the processing chamber.

As is apparent from the foregoing description, the charged particle beamprocessing system in accordance with the present invention and thepattern forming method using the same charged particle beam processingsystem irradiate the surface of a workpiece with a charged particle beamin an environment of a reactive gas to form a pattern by locallyprocessing portions of the surface of the workpiece irradiated with thecharged particle beam by reactive processing. Even if a highly corrosivereactive gas is used to form the pattern by etching a metal thin filmformed over the surface of the workpiece at a high etching rate, theworkpiece will not be corroded by the reaction of the reactive gas,which may otherwise be remaining on the surface of the workpiece, andmoisture contained in the atmosphere when the workpiece is taken outfrom the charged particle beam processing system into the atmosphere.

What is claimed is:
 1. A pattern forming method using a charged particlebeam process comprising: irradiating a workpiece with a focused chargedparticle beam in an environment of a reactive gas in a processingchamber for the local reactive processing of portions of the workpieceirradiated with the focused charged particle beam to form a pattern,wherein the reactive gas which is at least one of adsorbed by andadhered to a surface of the workpiece is removed from the surface of theworkpiece by heating the workpiece with one of a mercury vapor lamp andan infrared lamp in an environment of an inert gas in a load-lockchamber connected through a gate valve to the processing chamber, afterthe pattern has been formed in the processing chamber, by a reactive gasremoving process before taking out the workpiece from the load-lockchamber into the atmosphere.
 2. The pattern forming method using acharged particle beam process according to claim 1, wherein the one ofthe mercury vapor lamp and the infrared lamp is provided outside of theload-lock chamber so as to heat the workpiece by irradiation through atransparent window of the load-lock chamber.
 3. The pattern formingmethod using a charged particle beam process according to claim 1,wherein the reactive gas removing process which is carried out in theload-lock chamber includes heating the workpiece in an environment onthe order of 1×10−⁴ Pa in the load-lock chamber prior to exposing theworkpiece to the atmosphere.
 4. The pattern forming method using acharged particle beam process comprising: irradiating a workpiece with afocused charged particle beam in an environment of a reactive gas in aprocessing chamber for the local reactive processing of portions of theworkpiece irradiated with the focused charged particle beam to form apattern, wherein the reactive gas which is at least one of adsorbed byand adhered to a surface of the workpiece is removed from the surface ofthe workpiece by heating the workpiece with one of a mercury vapor lampand an infrared lamp in an environment of an inert gas in a load-lockchamber connected through a gate valve to the processing chamber, afterthe pattern has been formed in the processing chamber, by a reactive gasremoving process before taking out the workpiece from the load-lockchamber into the atmosphere, and wherein the reactive gas removingprocess is an irradiating process which irradiates the surface of theworkpiece with a focused charged particle beam in an environment ofoxygen gas.